Both the track ball and the mouse are popular peripheral devices of great importance to a computer. Especially, nowadays when the softwares such as WINDOWS and AUTO CAD are being widely-used, they are highly qualified for controlling a movement of a cursor shown on a monitor. However, there still exist individual limitations. It is necessary to prepare a larger space for operating the mouse on a flat surface. However, although a smaller space is required for operating the track ball, the moving speed of the cursor on the monitor will be slower and the user's fingers will easily get tired after a long operation time. Therefore, an individual apparatus combining therein a track ball and a mouse is accordingly developed.
A prior apparatus combining therein a track ball and a mouse, as disclosed in Taiwan, R.O.C. Patent Application No. 81,205,278 issued to Sysgration Ltd., comprises a shell 1, a ball 2 protruding through the shell 1, and a standing set 3 installed at the bottom of the shell 1, as shown in FIG. 1. The standing set 3 is similar to the one installed at the bottom of a computer keyboard for obtaining therefore an angle, e.g. 15.degree., between the keyboard surface and the desk surface. If the standing set 3 is flush with the bottom of the shell 1, the ball 2 can contact a flat surface such as a mouse pad so that the apparatus can function as a mouse, as shown in FIG. 2a. Otherwise, if the standing set 3 is turned to have an angle, e.g. 90.degree., with the bottom of the shell 1 to lift off the bottom of the shell 1 and the ball 2 from contacting a flat surface such as a desk surface, the apparatus can function as a track ball, as shown in FIG. 2b.
Even if the prior apparatus can function as both a track ball and a mouse, however, when the apparatus is used as a track ball, the standing set is easily unintentionally pressed back to its normal position to be flush with the bottom of the shell so that the lower part of the ball will contact the desk and the apparatus cannot function well as a track ball. In addition, the lower part of the ball protrudes and is exposed to the outside. Under this situation, if a user prefers holding this apparatus in one hand and rotates the ball with another hand, then the hand holding the apparatus will easily touch the ball which will adversely affect the rotation of the ball.
Furthermore, the ball of the prior apparatus, if the apparatus is used as a mouse, will be pushed upward so that the ball will be in a poor contact with the rollers. Although the prior apparatus further includes two magnetic pieces respectively installed beside two axial rods thereof so that two rollers provided on the axial rods can be attracted and pulled toward the ball, the problem of poor contact between the ball and the rollers is still unsolved.